could these two problems be related?

no luck so far in the a4 b5 forum, i'll try my luck here.

well i've been getting a p0171 code lately, on and off. I believe it's to do with the o2 sensor (how easily/often do these fail?)... but the definition lists a number of things, but I'm not sure where to start and kind of hesitant to start seeing as it's freezing outside and i haven't got a garage to work in.

Anyway, I've gotten an egg smell a few times, which usually indicates the catalytic converter.. could it be possible the problems related.. it makes sense to me. Any advice from anyone i will be greatly appreciated.

I've got an 01 a4 w/ 62k miles (which I believe means my cat is still under warranty.. should I just go to audi and have them look at it? think they'd charge me if it wasn't my cat?). I thought the code came up because I took apart my airbox, and putting it back together i think i lost something, because my secondary air pump feed doesn't want to reattach with the rubber part in there.. so it may be a little loose, would that cause the code?

Thanks!

egg smell can be too much fuel.  your code is for a lean system.  sounds to me like you could have a vacuum leak, putting in too much air, making the engine put in too much fuel causing your smell. id start there.  also, do you have a K&N filter on it?  if over oiled it could be contaminating your MAF causing a bad reading, making the engine think its lean.  its not necesarily a faulty O2 sensor.. could be, but not necesarly..

thanks for the reply. Yeah, I plan to look for a leak and do other no/low cost solutions first. no k&n.

If anyone else has anything else to say, please do.

I just bought my car 02 audi a4 1.8t and on my way home from the dealership my check engine light came on and when they checked it i had the same code. They told me to run the tank to empty and fill it up with 91 octane fuel i guess if you use lower octane it can mess with the O2 sensor. but the tech told me to see if that fixes the problem if not, then it could be spark plugs, MAF sensor, or O2 sensor and if not any of those then it might be my catalytic converter